Electrolysis device for producing iron with improved gas-permeable anode plate

Abstract

The invention relates to a device (1) for producing iron by reducing iron ore by means of an electrolytic reaction that releases gases, comprising a housing (4) comprising a gas-permeable anode plate (2) made of a porous material, a cathode plate (3), both facing one another and separated by an electrolyte chamber (6).

Description

[0001] The present invention relates to an apparatus for producing iron by an electrolytic process.

[0002] Steel can be produced on an industrial scale via two main manufacturing routes. Today, the most common production route is to produce pig iron in a blast furnace by reducing iron oxides using a reducing agent, mainly coke. In this process, about 450kg to 600kg of coke is consumed per ton of pig iron; this process releases large amounts of CO2 in the production of coke from coal in the coking plant and in the production of pig iron.

[0003] The second main route involves the so-called "direct reduction process". These include processes according to the MIDREX, FINMET, ENERGIRON / HYL, COREX, FINEX, etc. types, in which sponge iron in the form of HDRI (Hot Direct Reduced Iron), CDRI (Cold Direct Reduced Iron) or HBI (Hot Briquetted Iron) is produced by direct reduction of an iron oxide carrier. Sponge iron in the form of HDRI, CDRI and HBI usually undergoes further treatment in an electric arc furnace. Even though this second route emits less CO2 than the previous one, it still releases some CO2 and is moreover dependent on carbon fossil fuels.

[0004] Current developments are therefore focusing on methods that allow the carbon-neutral production of iron with less or even no CO2 release.

[0005] A known alternative method for producing steel from iron ore is based on electrochemical technology. In such a technology, iron is produced from iron oxide using an electrolytic cell unit comprising two electrodes, an anode and a cathode, connected to a current source, an electrolyte circuit and an iron oxide inlet leading to the electrolytic cell unit. The anode and cathode are always immersed in a circulating electrolyte to ensure good electrical conduction between the electrodes. The electrolytic reaction produces pure iron plates at the cathode and gaseous oxygen at the anode. The iron plates thus obtained can then be melted with other elements such as carbonaceous materials and / or melted as waste in an electric furnace to produce steel.

[0006] One of the problems of existing electrolytic cells is gas accumulation. In fact, the gas formed by the electrolysis reaction tends to remain trapped between the anode and the cathode, where the gas accumulates. Gaseous oxygen is an electrical insulator, which has an adverse effect on the electrical conduction between the electrodes and therefore on the productivity of the cell. One solution would be to continuously extract the electrolyte containing the gas, but this would mean a constant supply of fresh electrolyte, which would also be detrimental to the productivity and environmental footprint of the process.

[0007] Another solution is to have a permeable anode that allows the electrolyte to pass through, thereby extracting the gas from the space between the anode and the cathode. However, the permeability must be controlled so that the gas can be discharged continuously without interfering with the electrolysis reaction. Therefore, the object of the present invention is to remedy the disadvantages of the prior art by providing a gas-permeable anode that ensures improved extraction of the gas formed by the electrolysis reaction. The object of the present invention is also to provide an anode that is easy to manufacture and cost-effective.

[0008] For this purpose, the device of the invention comprises a housing comprising an anode plate and a cathode plate, both facing each other and separated by an electrolyte chamber, the housing being provided with means for circulating electrolyte in the electrolyte chamber and means for supplying iron ore to the electrolyte chamber, the housing also comprising a degassing unit comprising a gas recovery section extending along the side of the gas-permeable anode plate opposite to the chamber and capable of recovering gases from the electrolysis reaction escaping through the gas-permeable anode plate. According to the invention, the gas-permeable anode plate is made of a porous material comprising a plurality of compartments extending from the electrolyte flow chamber to the gas recovery section, each compartment being delimited by a circumferential wall and opening on two opposite sides of the gas-permeable anode plate.

[0009] The device of the present invention may also include the following optional features considered individually or in all possible technical combinations:

[0010] The compartments are repeated regularly and periodically on the gas-permeable anode plate.

[0011] - The circumferential wall of each compartment has a hexagonal cross section.

[0012] - Two adjacent compartments share one straight wall of their respective hexagonal circumferential walls.

[0013] - The hexagon formed by the hexagonal circumferential walls of each compartment is an equilateral hexagon.

[0014] An equilateral hexagon is defined according to the formula e / h<0.1, e being the thickness of the hexagonal wall and h being the distance between two opposite parallel straight walls of the hexagon.

[0015] The porous material forming the gas-permeable anode plate has a honeycomb structure.

[0016] The porous material of the gas-permeable anode plate is produced by welding a plurality of corrugated sheets to one another.

[0017] The housing comprises a cover plate facing the gas permeable anode plate, and the gas permeable anode plate comprises at least one T-shaped groove extending transversely along the side of the gas permeable anode plate opposite to the chamber and receiving a corresponding T-shaped rod. Fastening means pass through the cover plate up to the T-shaped rod, thereby holding the gas permeable anode plate at a desired distance from the cathode plate.

[0018] - The gas permeable anode plate is made of nickel alloy.

[0019] Other characteristics and advantages of the invention will become apparent from the following description, made by way of indication and not limitation, and with reference to the accompanying drawings, in which:

[0020] - Figure 1 Represents a longitudinal section of a device according to the invention,

[0021] - Figure 2 A three-dimensional diagram showing the porous material constituting the anode plate,

[0022] - Figure 3 express Figure 2 A top view of a porous material.

[0023] - Figure 4 Indicated by Figure 2 The anode plate is made of a block of porous material, and the anode plate is made of multiple such blocks.

[0024] - Figure 5 A longitudinal cross-sectional view of a portion of a housing according to the invention illustrating the fastening means of the anode plate in the housing.

[0025] - Figure 6 Represents the main production steps of a block of porous material.

[0026] First, it should be noted that in the drawings, the same reference numerals indicate the same elements regardless of the drawings in which they appear and regardless of the form in which they appear. Similarly, if the elements are not explicitly labeled in one of the drawings, the reference numerals for the elements can be easily found by referring to the elements themselves in another drawing.

[0027] It should also be noted that the drawings mainly represent one embodiment of the object of the invention, but that other embodiments corresponding to the definitions of the invention may exist.

[0028] Elements in the drawings are illustrative and may not be drawn to scale.

[0029] The present invention relates to a device 1, which is arranged to produce iron metal (Fe) by reducing iron ore, in particular containing hematite (Fe2O3) and other iron oxides or hydroxides, by electrolysis. The chemical reaction is well known and can be described by the following reaction formula (1):

[0030] (1)

[0031] It follows that the electrolysis reaction releases gases, primarily oxygen, which must be extracted from the device 1 .

[0032] Reference Figure 1 , the device 1 comprises a housing 4 extending along a longitudinal axis X, in which the electrolysis reaction takes place. Said housing 4 is delimited by a base plate 20, a cover plate 13 and two lateral plates 21. In addition, the housing 4 comprises a gas-permeable anode plate 2, intended to be completely immersed in an electrolyte 5, and a cathode plate 3, both facing each other and held at a desired distance by fastening means (not depicted in this figure). The housing 4 also comprises an electrolyte chamber 6, which extends longitudinally between the anode plate 2 and the cathode plate 3 as far as the exhaust chamber 22. The device 1 finally comprises a power supply (not depicted) connected to the anode plate 2 and the cathode plate 3.

[0033] To produce iron by electrolytic reaction, when the device 1 is in operation, an electrolyte 5, preferably a water-based solution, such as an aqueous sodium hydroxide solution, flows through the housing 4 in an electrolyte chamber 6. Therefore, the device 1 comprises means for circulating the electrolyte, which means may comprise an electrolyte circuit (not depicted) connected to an inlet 24 and an outlet 25, which are managed in the housing 4 and both are fluidly connected to the electrolyte chamber 6. The iron ore is preferably introduced into the device 1 through the inlet 24 as a powder suspension in the electrolyte 5.

[0034] During the electrolysis reaction, iron oxide is reduced to iron according to reaction (1), and the reduced iron is deposited on the cathode plate 3, while gaseous oxygen is released to the inside of the housing 4. Since these gases are electrical insulators, they hinder the good operation of the electrolysis reaction and must be continuously discharged to the outside of the housing 4.

[0035] For this purpose, the housing 4 comprises a degassing unit 7 comprising a gas recovery section 8 extending longitudinally along the side 27 of the anode plate 2 opposite the electrolyte chamber 6. The gas recovery section 8 is a compartment arranged to be filled with the electrolyte 5 and arranged between the anode plate 2 and the cover plate 13. Thus, the gas recovery section 8 is arranged to recover the gas escaping through the anode plate 2.

[0036] like Figure 1 , the degassing unit 7 further comprises an electrolyte recirculation section 28, which extends continuously with the gas recovery section 8 up to a gas outlet 29 managed in the housing 4. The electrolyte recirculation section 28 is arranged to be at least partially filled with electrolyte 5. In addition, said recirculation section 28 is fluidically connected to the electrolyte chamber 6. When the device 1 is in operation, the recirculation section 28 allows the electrolyte 5 flowing from the gas recovery section 8 to be redirected towards the electrolyte chamber 6 via, for example, an elbow 30 of the electrolyte recirculation section 28, which is adjacent to the anode plate 2 and fluidically connected to the electrolyte chamber 6.

[0037] Reference Figure 2 and Figure 3 And according to the invention, the gas permeable anode plate 2 is made of a porous material comprising a plurality of compartments 9. Each compartment 9 is delimited by a circumferential wall 10 and is open on two opposite sides of the anode plate 2, extending from the electrolyte chamber 6 to the gas recovery section 8 (see Figure 1 ). Such a configuration allows gas bubbles to flow through the anode plate 2 along with the electrolyte 5 for gas discharge.

[0038] All compartments preferably have the same height, and thus the anode has a constant thickness e A The thickness of the anode is A is defined as the distance between the top and bottom of the anode, the bottom side being the side facing the electrolyte chamber 6 and the top being the opposite side facing the gas recovery section 8. The thickness e of the anode A Preferably it is 5 mm to 50 mm, more preferably 10 mm to 20 mm. This allows to improve the gas discharge while maintaining a compact design of the device.

[0039] In addition to its role in venting gas bubbles, the gas permeable anode plate 2 must also contribute to a uniform electrolytic reaction to produce a consistent growth of iron deposits. In addition, the gas permeable anode plate 2 must be strong enough to withstand environmental conditions, in particular to withstand continuous immersion in the electrolyte and to continuously withstand the anode current. In particular, the electrolyte may include caustic soda at a concentration of 50% and fine iron oxide particles (10μm to 40μm diameter). The temperature inside the housing may be 100°C to 130°C. For a current intensity of about 1000A / m2, the power supplied to the electrodes may be 5VDC.

[0040] For this purpose, the porous material constituting the gas-permeable anode plate 2 preferably has a honeycomb structure, wherein compartments 9 are regularly and periodically repeated on the anode plate 2 for both gas discharge purposes and the purpose of conductive consistency. More precisely, each compartment 9 has a hexagonal cross section, and preferably each hexagon is an equilateral hexagon. This configuration provides perfect structural consistency, which increases the effective firmness of the anode plate and enhances electrical performance. In addition, this configuration maximizes the perimeter of each compartment 9 for better gas discharge.

[0041] Furthermore, two adjacent compartments 9 of the porous material are directly adjacent by sharing a common straight wall 11. Thus, with the exception of the compartments 9 located at the periphery of the anode plate 2, each compartment 9 is directly surrounded by six identical compartments 9. Such a configuration allows maximizing the number of gas exhaust compartments 9 while having a consistent metal thickness for enhancing electrical conduction. Such a configuration also plays a role in the robustness of the anode plate, since the forces to which the anode plate may be subjected are uniformly distributed over its entire surface.

[0042] exist Figure 4 and Figure 5 In the embodiment of the present invention, the anode plate 2 is made of a plurality of blocks 32, each of which is a quadrilateral plate made entirely of the above-mentioned porous material. In order to form the anode plate 2 and to keep each block 32 (and the resulting anode plate 2) at a desired distance from the cathode plate 3 in the device 1, a fastening device is used, which may include two T-shaped grooves 14, which are managed in the thickness of the block 32 and extend transversely along the side 27 of the block 32 opposite to the electrolyte chamber 6.

[0043] like Figure 5As shown above, each T-shaped groove 14 receives a T-shaped rod 15, which is inserted into the corresponding T-shaped groove 14 by sliding from one of its ends 31. When locked into the T-shaped groove 14, the T-shaped rod 15 cannot be extracted from the T-shaped groove 14 from the top. The fastening device 16 passes through the cover plate 13 along the corresponding hole until the T-shaped rod 15. Therefore, the block 32 is firmly held in the housing 4 at the desired distance from the cathode plate 3. This operation is repeated for each block 32. The number of blocks 32 is adjusted by a person skilled in the art according to the desired size of the anode plate 2.

[0044] Now refer to Figure 6 The method of manufacturing the block 32 is described. First, the metal sheet is pressed between toothed rollers 33. The resulting corrugated sheets 12 are welded together to form an initial block 34, which is cut by a cutter so that its thickness corresponds to the desired thickness of the anode plate 2, thereby providing a block 32 ready for assembly to form the anode plate 2 as described previously. Finally, the T-shaped grooves 14 can be machined to obtain Figure 4 Block 32( Figure 6 not depicted above).

[0045] This approach means the resulting anode plates are robust while being easy and cost-effective to implement.

[0046] The porous material and thus the anode plate are advantageously made of a nickel alloy, such as commercially available under the trade name 200 or Made of 201 nickel alloy.

[0047] In a preferred embodiment, the power source that powers the apparatus 1 uses renewable energy, which is defined as energy collected from renewable resources that are naturally replenished on a human time scale, including sources such as sunlight, wind, rain, tides, waves, and geothermal heat. In some embodiments, electricity from nuclear sources can be used because nuclear sources do not emit CO2 to be produced. This further limits the CO2 footprint of the iron production process.

[0048] Example

[0049] Each block consists of 32 200 or 201. The porous material is made of the honeycomb structure as described above. The thickness e of the hexagonal wall 10 of each cell 9 is 0.25 mm, and the distance h between the two opposite parallel straight walls 11 of one cell 9 is 3.175 mm. Therefore, the ratio between the thickness e and the distance h is 0.079.

[0050] The dimensions of each block 32 are as follows:

[0051] -Height: 20mm+ / -0.5mm

[0052] -Width: 250mm+ / -0.5mm

[0053] -Length: 250mm+ / -0.5mm

[0054] Each block 32 is constructed using Figure 6 obtained by the previously described method illustrated in FIG.

[0055] The anode plate 2 is made of 44 blocks so that the resulting surface of the anode plate 2 is 2.75 m 2 .

[0056] The anode plate according to the invention promotes good discharge of gases to the outside of the electrolyte chamber and thus achieves good productivity of the electrolyte chamber while being easy to manufacture and cost-effective.

Claims

1. A device (1) for producing iron by reducing iron ore using an electrolytic reaction, the electrolytic reaction releasing gas, the device comprising a housing (4), the housing (4) comprising a gas-permeable anode plate (2), a cathode plate (3), the gas-permeable anode plate (2) and the cathode plate (3) both facing each other and separated by an electrolyte chamber (6), The housing (4) is provided with means (24, 25) for circulating electrolyte (5) in the electrolyte chamber (6) and means (24) for supplying iron ore to the electrolyte chamber (6), The housing (4) further comprises a degassing unit (7), the degassing unit (7) comprising a gas recovery section (8) extending along a side of the gas permeable anode plate (2) opposite to the chamber (6) and capable of recovering gas from the electrolysis reaction escaping through the gas permeable anode plate (2), The gas permeable anode plate (2) is made of a porous material comprising a plurality of compartments (9) extending from the electrolyte chamber (6) to the gas recovery section (8), each compartment (9) being delimited by a circumferential wall (10) and open on two opposite sides of the gas permeable anode plate (2).

2. The device according to claim 1, wherein: The compartments (9) are repeated regularly and periodically on the gas-permeable anode plate (2).

3. The device according to any one of claims 1 and 2, wherein: The circumferential wall (10) of each compartment (9) has a hexagonal cross section.

4. The device according to claim 3, wherein: Two adjacent compartments (9) share one straight wall (11) among their respective hexagonal circumferential walls (10).

5. The device according to any one of claims 3 and 4, wherein: The hexagon formed by the hexagonal circumferential walls of each compartment (9) is an equilateral hexagon.

6. The device according to claim 5, wherein: The equilateral hexagon is defined according to the formula e / h<0.1, e being the thickness of the hexagonal wall (10) and h being the distance between two opposite parallel straight walls (11) of the hexagon.

7. Apparatus according to any one of the preceding claims, wherein: The porous material forming the gas permeable anode plate (2) has a honeycomb structure.

8. The device according to any one of claims 3 to 7, wherein: The porous material of the gas-permeable anode plate (2) is produced by welding a plurality of corrugated sheets (12) to one another.

9. The device according to any one of the preceding claims, wherein: The housing (4) comprises a cover plate (13) facing the gas permeable anode plate (2), wherein the gas permeable anode plate (2) comprises at least one T-shaped groove (14) extending transversely along the side of the gas permeable anode plate (2) opposite to the chamber (6) and receiving a corresponding T-shaped rod (15), and wherein a fastening device (16) passes through the cover plate (13) up to the T-shaped rod (15) to maintain the gas permeable anode plate (2) at a desired distance from the cathode plate (3).

10. The device according to any one of the preceding claims, wherein The gas permeable anode plate (2) is made of a nickel alloy.

11. The device according to any one of the preceding claims, wherein The device is powered by renewable energy.

12. Apparatus according to any one of the preceding claims, wherein: The gas permeable anode plate (2) has a thickness of 5 mm to 50 mm. A .

Images